Power reception device and power reception method for non-contact power transmission

ABSTRACT

A power reception control device provided in a power reception device of a non-contact power transmission system includes a power-reception-side control circuit that controls an operation of the power reception device, and a power supply control signal output terminal that supplies a power supply control signal to a charge control device, the power supply control signal controlling power supply to a battery. The power-reception-side control circuit controls a timing at which the power supply control signal (ICUTX) is output from the power supply control signal output terminal. The operation of the charge control device is compulsorily controlled using the power supply control signal (ICUTX).

This is a Continuation of application Ser. No. 15/581,534 filed Apr. 28,2017, which in turn is a Continuation of application Ser. No. 14/928,414filed Oct. 30, 2015 and issued as U.S. Pat. No. 9,673,636 filed Jun. 6,2017, which in turn is a Continuation of application Ser. No. 14/467,792filed Aug. 25, 2014 and issued as U.S. Pat. No. 9,209,636 on Dec. 8,2015, which in turn is a Continuation of application Ser. No. 13/689,240filed Nov. 29, 2012 and issued as U.S. Pat. No. 8,836,273 on Sep. 16,2014, which in turn is a Continuation of application Ser. No. 12/174,305filed Jul. 16, 2008 and issued as U.S. Pat. No. 8,344,688 on Jan. 1,2013, which claims priority of Japanese Patent Application No.2007-186109 filed on Jul. 17, 2007. The disclosures of these priorapplications are hereby incorporated by reference herein in theirentirety.

BACKGROUND OF THE INVENTION

The present invention relates to a power reception control device, apower reception device, a non-contact power transmission system, acharge control device, a battery device, and an electronic instrument.

In recent years, non-contact power transmission (contactless powertransmission) that utilizes electromagnetic induction to enable powertransmission without metal-to-metal contact has attracted attention. Asapplication examples of non-contact power transmission, charging aportable telephone, charging a household appliance (e.g., cordlesstelephone handset or watch), and the like have been proposed.

JP-A-2006-60909 discloses a non-contact power transmission device usinga primary coil and a secondary coil, for example. JP-A-2006-166619discloses the circuit configuration of a charging device for a secondarybattery (e.g., lithium-ion battery), for example.

Since a related-art non-contact power transmission device is configuredso that a power-reception-side control circuit merely has a powerreception function and a function of controlling power supplied to abattery (e.g., battery pack), a dedicated charge control circuitcontrols a charging current (and a charging voltage) supplied to thebattery.

According to this configuration, the non-contact power transmissionsystem cannot positively control the charging current (charging voltage)supplied to the battery. Therefore, the functions that can beimplemented are limited.

It is important to take measures against a foreign object in order toimprove the safety and the reliability of the non-contact powertransmission system. Specifically, when power is transmitted in a statein which a metal foreign object is present, abnormal heat generation mayoccur. In this case, power transmission must be stopped. A metal foreignobject may be small or medium-sized, or may be large (e.g., a thin sheetwhich is present over the entire area between a primary-side instrumentand a secondary-side instrument). Therefore, it is desirable to takeappropriate safety measures irrespective of the size or type of foreignobject.

For example, when a thin sheet-shaped metal foreign object is insertedto completely block a primary-side instrument and a secondary-sideinstrument during power transmission, the primary-side instrument devicemay erroneously regard the metal foreign object as the secondary-sideinstrument and continue power transmission. Such an erroneous powertransmission state is hereinafter referred to as “takeover state”. It isdifficult to detect the takeover state using related-art technology.

SUMMARY

According to one aspect of the invention, there is provided a powerreception control device provided in a power reception device, the powerreception device being included in a non-contact power transmissionsystem that performs non-contact power transmission from a powertransmission device to the power reception device through a primary coiland a secondary coil that are electromagnetically coupled, the powerreception device supplying power to a battery device, the powerreception control device comprising:

a power-reception-side control circuit that controls an operation of thepower reception device; and

a power supply control signal output terminal that supplies a powersupply control signal to the battery device, the power supply controlsignal controlling power supplied to the battery device,

the power-reception-side control circuit controlling a timing at whichthe power supply control signal is output from the power supply controlsignal output terminal.

According to another aspect of the invention, there is provided a powerreception device comprising:

a power reception section that converts an induced voltage in thesecondary coil into a direct-current voltage;

the above power reception control device; and

an output terminal that outputs a power supply control signal outputfrom the power reception control device to a battery device.

According to another aspect of the invention, there is provided anelectronic instrument comprising:

the above power reception device; and

a battery device that receives power from the power reception device.

According to another aspect of the invention, there is provided anon-contact power transmission system comprising:

a power transmission device;

a primary coil;

a secondary coil;

a power reception device including the above power reception controldevice; and

a battery device that receives power from the power reception device.

According to another aspect of the invention, there is provided a chargecontrol device included in a battery device as a power supply target ofa non-contact power transmission system,

the charge control device receiving power supplied from a powerreception device of a non-contact power transmission system, andcontrolling charging of a battery included in the battery device,

the operation of the charge control device that controls charging of thebattery being controlled using a power supply control signal output fromthe power reception device.

According to another aspect of the invention, there is provided abattery device comprising:

the above charge control device; and

a battery, charging of the battery being controlled by the chargecontrol device.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIGS. 1A to 1C are views illustrative of examples of an electronicinstrument to which non-contact power transmission technology isapplied, and the principle of non-contact power transmission using aninduction transformer.

FIG. 2 is a view illustrative of load power supply control performed bya power reception device.

FIG. 3 is a circuit diagram showing an example of a specificconfiguration of each section of a non-contact power transmission systemthat includes a power transmission device and a power reception device.

FIGS. 4A and 4B are views illustrative of the principle of informationtransmission between a primary-side instrument and a secondary-sideinstrument.

FIGS. 5A and 5B are cross-sectional views of electronic instruments thatform a non-contact power transmission system which are illustrative offoreign object insertion (takeover state) after normal powertransmission has started.

FIGS. 6A and 6B are views illustrative of a specific embodiment whenintermittently changing a load of a power reception device so thatinsertion of a foreign object can be detected.

FIG. 7 is a circuit diagram showing an outline of the configuration of anon-contact power transmission system having a function of detecting atakeover state.

FIGS. 8A and 8B are views illustrative of a specific preferredembodiment of load modulation that enables foreign object detection.

FIGS. 9A to 9E are views illustrative of a battery load reductionoperation.

FIGS. 10A and 10B are views illustrative of a load modulation timing anda load reduction timing.

FIGS. 11A and 11B are views illustrative of an example of battery chargecontrol (example that uses a current regulation resistor).

FIG. 12 is a circuit diagram showing an example of the internal circuitconfiguration of the main portion of a charger (charge control IC) shownin FIG. 11A.

FIG. 13 is a circuit diagram illustrative of an example of a specificinternal configuration and operation of a charge control device.

FIG. 14 is a circuit diagram illustrative of another example of aspecific internal configuration and operation of a charge controldevice.

FIG. 15 is a flowchart showing an outline of an example of the operationof a power transmission device.

FIG. 16 is a circuit diagram showing an example of the configuration ofa power-transmission-side control circuit.

FIG. 17 is a view showing a basic sequence example of a non-contactpower transmission system.

FIG. 18 is a state transition diagram showing the state transition of anon-contact power transmission system that performs the sequence shownin FIG. 17.

FIG. 19 is a flowchart showing an operation example of a non-contactpower transmission system that performs the basic sequence shown in FIG.17.

FIG. 20 is a flowchart showing an operation example of a non-contactpower transmission system that performs the basic sequence shown in FIG.17.

FIG. 21 is a view illustrative of the principle of position detection.

FIGS. 22A to 22F are views illustrative of the principle of metalforeign object (conductive foreign object) detection.

FIGS. 23A to 23D are views illustrative of the principle of removaldetection.

DETAILED DESCRIPTION OF THE EMBODIMENT

At least one embodiment of the invention may enable a non-contact powertransmission system (power-reception-side control circuit) to positivelycontrol a charging current (charging voltage) supplied to apower-supply-target load (e.g., battery), for example.

At least one embodiment of the invention may enable detection of atakeover state by causing a power-reception-side (secondary-side)instrument to perform intermittent load modulation. At least oneembodiment of the invention may also enable a power-transmission-side(primary-side) instrument to easily detect load modulation by reducingthe load state of the power-supply-target load (e.g., battery) whenperforming load modulation, whereby the takeover state detectionaccuracy may be improved, for example.

(1) According to one embodiment of the invention, there is provided apower reception control device provided in a power reception device, thepower reception device being included in a non-contact powertransmission system that performs non-contact power transmission from apower transmission device to the power reception device through aprimary coil and a secondary coil that are electromagnetically coupled,the power reception device supplying power to a battery device, thepower reception control device comprising:

a power-reception-side control circuit that controls an operation of thepower reception device; and

a power supply control signal output terminal that supplies a powersupply control signal to the battery device, the power supply controlsignal controlling power supplied to the battery device,

the power-reception-side control circuit controlling a timing at whichthe power supply control signal is output from the power supply controlsignal output terminal.

The battery device as the power supply target of the non-contact powertransmission system includes a battery and a charge control device(e.g., charge control IC) that controls charging of the battery, forexample.

The power reception control device (e.g., power reception device controlIC) that controls the operation of the power reception device of thenon-contact power transmission system can output the power supplycontrol signal (ICUTX) to the charge control device (e.g., chargecontrol IC) that controls charging of the battery, for example.Therefore, the power reception control device that controls theoperation of the power reception device of the non-contact powertransmission system can positively take part in the operation ofcharging the battery as the power-supply-target load.

The power supply control signal (ICUTX) is output from the power supplycontrol signal output terminal provided in the power reception controldevice, and the output timing of the power supply control signal (ICUTX)is controlled by the power-reception-side control circuit. This functionenables a novel operation.

For example, when the charge control device does not operate normally,the charging current can be adjusted by externally controlling the powersupply function of the charge control device using the power supplycontrol signal (ICUTX).

The power transmission device may issue a battery control command to thepower reception device, and the power reception control device maycontrol power supplied to the battery using the power supply controlsignal (ICUTX).

For example, when charging the battery which has been consumed to alarge extent, the charging time can be reduced by increasing thecharging current using the power supply control signal (ICUTX) in theinitial charging stage.

When the power reception device transmits a signal to the powertransmission device by means of load modulation, a situation in whichcharging of the battery hinders communication by means of loadmodulation can be prevented by reducing (or stopping) the chargingcurrent supplied to the battery using the power supply control signal(ICUTX). A takeover state (e.g., a state in which a thin sheet-shapedmetal foreign object is inserted between the primary coil and thesecondary coil to block electromagnetic coupling between the primarycoil and the secondary coil) can be reliably detected by the powertransmission device by utilizing the above-described function.

Since the power reception control device controls power supplied to thebattery through the charge control device, the power reception controldevice need not include a power supply limiting means or the like. Thismakes it unnecessary to provide an additional circuit. Therefore, thepower reception control device can be implemented by a minimum circuitconfiguration.

Since power supplied to the battery is controlled through the chargecontrol device provided at a position closest to the battery (e.g.,secondary battery), highly accurate power supply control can beimplemented. For example, charge control with higher accuracy can beeasily implemented by utilizing the charge control function (e.g.,charging current regulation function or negative feedback controlfunction) of the charge control device.

(2) In the power reception control device according to this embodiment,

the battery device may include a battery and a charge control devicethat controls charging of the battery; and

the resistance of a current regulation resistor that adjusts a chargingcurrent supplied to the battery may be controlled using the power supplycontrol signal output from the power reception control device so thatthe charging current supplied to the battery is adjusted.

This embodiment illustrates an example of battery power supply controlperformed using the power supply control signal (signal ICUTX). In thisembodiment, the resistance of the current regulation resistor iscontrolled using the power supply control signal (signal ICUTX). Powersupplied to the battery can be externally controlled by a simpleconfiguration. The current regulation resistor may be an internalresistor (e.g., a resistor provided in the charge control IC), or may bean external resistor (e.g., a resistor externally connected to aresistor connection terminal of the charge control IC).

(3) In the power reception control device according to this embodiment,

the current regulation resistor may be an external resistor, and acontrol element that changes the resistance of the current regulationresistor as the external resistor may be provided in the charge controldevice; and

the power supply control signal may control an operation of the controlelement to adjust the resistance of the current regulation resistor asthe external resistor.

Specifically, an external resistor is used as the current regulationresistor, and the resistance of the external resistor is controlledusing the control element. According to this configuration, powersupplied to the battery can be controlled using the power supply controlsignal (signal ICUTX) without changing the internal circuitconfiguration of the charge control IC included in the charge controldevice, for example.

Moreover, control such as changing the charging current in a pluralityof stages can be easily implemented by merely changing the configurationof an external circuit, for example.

(4) In the power reception control device according to this embodiment,

the battery device may include a battery and a charge control devicethat controls charging of the battery;

the charge control device may control a charging current or a chargingvoltage supplied to the battery to be set at a desired value using anegative feedback control circuit; and

the power supply control signal output from the power reception controldevice may control an operation of the negative feedback control circuitincluded in the charge control device to adjust the charging current.

The operation of the negative feedback control circuit included in thecharge control device is controlled using the power supply controlsignal (ICUTX) to compulsorily control the charging current supplied tothe battery. The amount of the charging current can be controlled withhigh accuracy by utilizing negative feedback control. Moreover, theamount of the charging current can be finely adjusted.

(5) In the power reception control device according to this embodiment,

the battery device may include a battery and a charge control devicethat controls charging of the battery;

the charge control device may include a power supply regulation circuitprovided in a power supply path connected to the battery; and

the power supply control signal output from the power reception controldevice may control an operation of the power supply regulation circuitto adjust the charging current.

In this embodiment, the power supply regulation circuit is provided inthe power supply path of the charge control device, and the power supplyregulation circuit is operated using the power supply control signal(ICUTX) to reduce (or temporarily stop) power supplied to the batterydevice, for example. Since power supply through the power supply path isdirectly controlled, complicated control is unnecessary. Moreover, theinternal circuit does not become complicated.

(6) In the power reception control device according to this embodiment,

the power reception control device may further include a load modulationsection that modulates a load of the power reception device,

the power-reception-side control circuit may cause the load modulationsection to intermittently change the load of the power reception devicewhen power is supplied to the battery device through the charge controldevice, and may output the power supply control signal from the powersupply control signal output terminal to reduce or stop power suppliedto the battery device in a period in which the load of the powerreception device is intermittently changed.

Specifically, power supplied to the battery device is reduced or stoppedusing the power supply control signal (ICUTX) in synchronization withintermittent load modulation performed by the power reception device.The power reception device performs load modulation intermittently(e.g., cyclically or regularly). Load modulation is performed by causinga load-modulation transistor to be turned ON/OFF, for example.

The power transmission device detects intermittent load modulationperformed by the power reception device. If intermittent load modulation(change in load) cannot be detected, the power transmission devicedetermines that a takeover state (i.e., a state in which a metal foreignobject takes over power transmitted from the power transmission device)has occurred.

When the load state of the battery (i.e., power-supply-target load) isheavy (i.e., when a large amount of charging current flows), it isdifficult for the power transmission device to detect a change in coilend voltage of the primary coil due to intermittent load modulation, forexample.

Therefore, the power transmission device can reliably receive a loadmodulation signal by reducing the load of the battery in a period (loadmodulation period) in which the power reception device performs loadmodulation. The load reduction process may be performed only when theload of the battery is heavy, or may be necessarily performed insynchronization with a load modulation period. The load may also bereduced by reducing or temporarily stopping the charging currentsupplied to the battery.

(7) In the power reception control device according to this embodiment,

the power-reception-side control circuit may create a load reductionperiod in which power supplied to the battery device is reduced orstopped due to output of the power supply control signal, and may causethe load modulation section to perform load modulation during the loadreduction period.

Specifically, the load reduction period is created using the powersupply control signal (ICUTX), and the load is modulated during (partof) the load reduction period In the load reduction period, the chargingcurrent supplied to the battery is reduced (or stopped) so that the loadstate of the battery (i.e., power-supply-target load) is reduced.Therefore, when the power reception device performs load modulation(e.g., momentarily increases the load of the power reception device),the power transmission device can reliably detect a change in coil endvoltage (or coil end current) of the primary coil due to loadmodulation. This improves the regular load authentication accuracy.

(8) According to another embodiment of the invention, there is provideda power reception device comprising:

a power reception section that converts an induced voltage in thesecondary coil into a direct-current voltage;

the above power reception control device; and

an output terminal that outputs a power supply control signal outputfrom the power reception control device to a battery device.

This embodiment specifies the configuration of the power receptiondevice (provided with the power reception control device according tothe invention). When the power reception control device is an IC, thepower reception device may be implemented as a module that includes theIC, for example. The power reception device also includes a terminalthat outputs the power supply control signal (ICUTX).

(9) According to another embodiment of the invention, there is providedan electronic instrument comprising:

the above power reception device; and

a battery device that receives power from the power reception device.

The electronic instrument according to this embodiment has a function ofdirectly controlling the battery to implement various operationsdiffering from those implemented by related art. Therefore, theelectronic instrument including the power reception device has highperformance, a reduced size, and excellent reliability and safety.

(10) According to another embodiment of the invention, there is provideda non-contact power transmission system comprising:

a power transmission device;

a primary coil;

a secondary coil;

a power reception device including the above power reception controldevice; and

a battery device that receives power from the power reception device.

According to this embodiment, a novel non-contact power transmissionsystem that can externally and directly control the charge state of thebattery device (e.g., including a charge control device and a battery asthe power-supply-target load).

(11) According to another embodiment of the invention, there is provideda charge control device included in a battery device as a power supplytarget of a non-contact power transmission system,

the charge control device receiving power supplied from a powerreception device of a non-contact power transmission system, andcontrolling charging of a battery included in the battery device,

the operation of the charge control device that controls charging of thebattery being controlled using a power supply control signal output fromthe power reception device.

Specifically, a configuration example of the charge control deviceconforming to a novel non-contact power transmission system isspecified. The charge control device includes a power supply controlsignal input terminal to which the power supply control signal is input.

(12) In the charge control device according to this embodiment,

the resistance of a current regulation resistor that adjusts a chargingcurrent supplied to the battery may be controlled using the power supplycontrol signal.

The amount of charging current (power) supplied to the battery can beprogrammed using the current regulation resistor. Power supplied to thebattery can be compulsorily and externally controlled using the powersupply control signal (ICUTX) by positively utilizing theabove-described function.

(13) In the charge control device according to this embodiment,

the current regulation resistor may be an external resistor, and acontrol element that changes the resistance of the current regulationresistor as the external resistor may be provided in the charge controldevice; and

an operation of the control element may be controlled using the powersupply control signal so that the resistance of the current regulationresistor as the external resistor is adjusted.

Specifically, an external resistor is used as the current regulationresistor, and the resistance of the external resistor is controlledusing the control element. According to this configuration, powersupplied to the battery can be controlled using the power supply controlsignal (signal ICUTX) without changing the internal circuitconfiguration of the charge control IC included in the charge controldevice. Moreover, control such as changing the charging current in aplurality of stages can be easily implemented by merely changing theconfiguration of an external circuit, for example.

(14) In the charge control device according to this embodiment,

the charge control device may include a negative feedback controlcircuit, the negative feedback control circuit controlling a current ora voltage supplied to the battery to be set at a desired value,

an operation of the negative feedback control circuit included in thecharge control device may be controlled using the power supply controlsignal.

The operation of the negative feedback control circuit included in thecharge control device is controlled using the power supply controlsignal (ICUTX) to compulsorily control the charging current supplied tothe battery. The amount of the charging current can be controlled withhigh accuracy by utilizing negative feedback control. Moreover, theamount of the charging current can be finely adjusted.

(15) In the charge control device according to this embodiment,

the charge control device may include a power supply regulation circuitprovided in a power supply path connected to the battery,

an operation of the power supply regulation circuit may be controlledusing the power supply control signal.

In the charge control device according to this embodiment, the powersupply regulation circuit is provided in the power supply path, andpower supplied to the battery is reduced or stopped using the powersupply control signal (ICUTX). Since power supply through the powersupply path is directly controlled, complicated control is unnecessary.Moreover, the internal circuit does not become complicated.

(16) According to another embodiment of the invention, there is provideda battery device comprising:

the above charge control device; and

a battery, charging of the battery being controlled by the chargecontrol device.

The battery device includes the charge control device and the battery(e.g., secondary battery). As an example of the battery device, asecondary battery pack including a charge control IC may be mentioned,for example. The term “battery” also includes a battery having a chargecontrol function.

Preferred embodiments of the invention are described below withreference to the drawings. Note that the following embodiments do not inany way limit the scope of the invention defined by the claims laid outherein. Note that all elements of the following embodiments should notnecessarily be taken as essential requirements for the invention.

First Embodiment Examples of an electronic instrument to which theinvention is suitably applied and the principle of non-contact powertransmission technology are described below.

Examples of Electronic Instrument and Principle of Non-Contact PowerTransmission

FIGS. 1A to 1C are views illustrative of examples of an electronicinstrument to which the non-contact power transmission technology isapplied, and the principle of non-contact power transmission using aninduction transformer.

As shown in FIGS. 1A and 1B, a charger (cradle) 500 (i.e.,power-transmission-side electronic instrument) includes a powertransmission device (e.g., power transmission module including apower-transmission-side control circuit (power-transmission-side controlIC)) 10.

The charger (cradle) 500 also includes a switch (SW) that causes(triggers) power transmission to start or stop, and a display section(e.g., LED) 16 that is turned ON when the charger transmits power(operates). Note that the switch (SW) may not be provided.

In the charger (cradle) 500 shown in FIG. 1A, the switch (SW) isprovided outside an area in which a power-reception-side electronicinstrument (portable telephone) 510 is placed. When the user who desiresto charge the portable telephone 510 has pressed the switch (SW) withthe finger, the power transmission device 10 starts power transmission(temporary power transmission for position detection and IDauthentication: described later). When the switch (SW) has been pressedduring power transmission (including temporary power transmission andnormal power transmission), power transmission is necessarily(compulsorily) stopped.

As the switch (SW), a mechanical momentary switch may be used, forexample. Note that the switch (SW) is not limited thereto. Variousswitches such as a relay switch and a magnet switch may also be used.

In the charger (cradle) 500 shown in FIG. 1B, the switch (SW) isprovided inside an area in which the power-reception-side electronicinstrument (portable telephone) 510 is placed. Therefore, when theportable telephone 510 is placed on the charger (cradle) 500, the switch(SW) is automatically pressed (turned ON) due to the weight of thecharger (cradle) 500. This causes the charger (cradle) 500 to startpower transmission (temporary power transmission for position detectionand ID authentication: described later).

When the switch (SW) has been pressed during power transmission(including temporary power transmission and normal power transmission)(e.g., when the portable telephone 510 has been removed from the charger(cradle) 500 and then placed on the charger (cradle) 500 so that theswitch (SW) has been pressed again), power transmission is necessarilystopped.

In FIG. 1B, the switch (SW) causes power transmission to start in thesame manner as in FIG. 1A, but is not used to detect the presence of theportable telephone 510 (removal of the portable telephone 510 isbasically determined based on an induced voltage in a primary coil:described later). Note that the switch (SW) may also have a function ofdetecting the presence of the portable telephone 510.

The portable telephone 510 (i.e., power-reception-side electronicinstrument) includes a power reception device (e.g., power transmissionmodule including a power-reception-side control circuit(power-reception-side control IC)) 40. The portable telephone 510 alsoincludes a display section 512 (e.g., LCD), an operation section 514that includes a button or the like, a microphone 516 (sound inputsection), a speaker 518 (sound output section), and an antenna 520.

Power is supplied to the charger 500 through an AC adaptor 502. Thepower supplied to the charger 500 is transmitted from the powertransmission device 10 to the power reception device 40 by means ofnon-contact power transmission. This makes it possible to charge abattery of the portable telephone 510 or operate a device provided inthe portable telephone 510.

As schematically shown in FIG. 1C, power transmission from the powertransmission device 10 to the power reception device 40 is implementedby electromagnetically coupling a primary coil L1(power-transmission-side coil) provided in the power transmission device10 and a secondary coil L2 (power-reception-side coil) provided in thepower reception device 40 to form a power transmission transformer. Thisenables non-contact power transmission.

Note that the switch (SW) is not an indispensable element. The switch(SW) need not necessarily be provided when the presence of the portabletelephone (power-reception-side instrument) 510 can be detected.

Note that the electronic instrument to which this embodiment is appliedis not limited to the portable telephone 510. For example, thisembodiment may be applied to various electronic instruments such as awristwatch, a cordless telephone, a shaver, an electric toothbrush, awrist computer, a handy terminal, a portable information terminal, and apower-assisted bicycle.

Examples of particularly suitable electronic instruments include aportable terminal (including a portable telephone terminal, PDAterminal, and portable personal computer terminal) and a watch. Sincethe power reception device according to the invention has a simpleconfiguration and a reduced size, the power reception device can beincorporated in a portable terminal or the like. The charging time of asecondary battery provided in an electronic instrument can be reducedusing the power reception device according to the invention due to lowloss. Moreover, since the power reception device according to theinvention reduces heat generation, the reliability of an electronicinstrument is improved from the viewpoint of safety.

In particular, since a large amount of charging current flows through aportable terminal (including a portable telephone terminal, PDAterminal, and portable personal computer terminal) under heavy load,heat may be generated to a large extent. A watch is an instrument forwhich a reduction in size and power consumption is strongly demanded.Therefore, it is important to reduce loss when charging a battery.Therefore, the features of the invention (i.e., low loss and low heatgeneration) can be sufficiently utilized for these instruments.

Load Control Using Power Reception Device

In this embodiment, the power reception device (secondary-side device(e.g., module device) that receives power from the power transmissiondevice) positively controls power supplied to a battery (e.g., secondarybattery) provided in a battery device (e.g., battery pack). This featureis described below.

FIG. 2 is a view illustrative of load power supply control performed bythe power reception device. The power transmission device 10 transmitspower to the power reception device 40 by means of non-contact powertransmission through the primary coil (L1) and the secondary coil (L2).The power reception device 40 operates using power transmitted from thepower transmission device 10, and supplies power to a charge controldevice (the charge control device acts as a load since the chargecontrol device consumes power).

A charge control device 92 is a dedicated IC that controls charging of abattery 94, for example. The charge control device 92 and the battery 94may be separate (independent) components, or may be integrally providedas a battery device 90.

The following description is given on the assumption that the chargecontrol device 92 and the battery 94 are provided in the battery device90 (note that the invention is not limited thereto). The entire batterydevice 90 may be considered to be a load (may be referred to as thebattery device 90). The battery 94 acts as a power-supply-target load.

As shown in FIG. 2, the power reception device (e.g., module device) 40includes power terminals (TA1 and TA2) that supply power supply voltages(VDD and VSS) to the battery device 90, a terminal (TA3) that receives acharge detection signal (LEDR) from the battery device 90, and an outputterminal (TA4) that supplies a power supply control signal (ICUTX) tothe battery device 90.

The power reception device 40 includes a power reception control device(IC) 50. The power reception control device (IC) 50 includes twoterminals TB1 and TB2. The terminal TB1 is a power supply control signaloutput terminal that outputs the power supply control signal (ICUTX),and the terminal TB2 is a terminal that receives the charge detectionsignal (LEDR).

The power reception device 40 includes the four terminals TA1 to TA4.The terminals TA1 and TA2 are power supply (VDD and VSS) terminals, theterminal TA4 is a power supply control signal output terminal thatoutputs the power supply control signal (ICUTX), and the terminal TA3 isa terminal that receives the charge detection signal (LEDR).

The battery device 90 includes four nodes (TA5 to TA8) respectivelyprovided corresponding to the terminals (TA1 to TA4) of the powerreception device 40, the battery (e.g., secondary battery) 94, and thecharge control device 92 (including a current control means 93, forexample).

The power supply control signal (ICUTX) controls the operation of thecurrent control means 93 provided in the charge control device 92, forexample, whereby power (charging current Iload) supplied to the battery94 is compulsorily controlled. The configuration and the operation ofthe current control means 93 are described later with reference to FIGS.11 to 14. The current control means 93 may be provided in a chargecontrol IC included in the charge control device 92, or may be providedoutside the charge control IC as an external adjustment means.

Since the power reception device 40 can compulsorily control the batterydevice 90 with regard to the function of supplying power to the battery,various operations differing from those implemented by related art canbe implemented. For example, the following novel operations can beachieved.

(1) For example, when the charge control device 92 does not operatenormally, the charging current can be adjusted by externally controllingthe power supply function of the charge control device 92 (i.e., theoperation of the current control means 93) using the power supplycontrol signal (ICUTX).

(2) The operation of the battery device 90 with regard to power suppliedto the battery 94 can be controlled by causing the power transmissiondevice 10 to issue a battery control command to the power receptiondevice 40.

(3) A special charge mode differing from normal charge operation can beimplemented by positively utilizing the power supply control signal(ICUTX). For example, when charging the battery 94 which has beenconsumed to a large extent, the charging time can be reduced byincreasing the amount of current received by the battery 94 in an earlystage of charging.

(4) When the power reception device 40 transmits a signal to the powertransmission device 10 by means of load modulation, a situation in whichcharging of the battery hinders communication by means of loadmodulation can be prevented by reducing (or stopping) the chargingcurrent (Iload) supplied to the battery 94 using the power supplycontrol signal (ICUTX).

(5) A takeover state (e.g., a state in which a thin sheet-shaped metalforeign object is inserted between the primary coil and the secondarycoil to block electromagnetic coupling between the primary coil and thesecondary coil) can be reliably detected by the power transmissiondevice 10 by utilizing the function described in (4).

(6) Since power supplied to the battery is controlled through the chargecontrol device 92 provided in the battery device 90, it is unnecessaryto provide an additional circuit. Therefore, it suffices to provide aminimum circuit configuration.

(7) Since power supplied to the battery is controlled through the chargecontrol device 92 provided at a position closest to the battery (e.g.,secondary battery) 94, highly accurate power supply control can beimplemented. Charge control with higher accuracy can be easilyimplemented by utilizing the charge control function (e.g., chargingcurrent negative feedback control function) of the charge control device92.

Specific Examples of Configurations of Power Transmission Device andPower Reception Device

FIG. 3 is a circuit diagram showing an example of a specificconfiguration of each section of a non-contact power transmission systemthat includes the power transmission device and the power receptiondevice.

As shown in FIG. 3, the power transmission device 10 includes a powertransmission control device 20, a power transmission section 12, and awaveform monitoring circuit 14. The power transmission control device 20includes a power-transmission-side control circuit 22, an oscillationcircuit 24, a driver control circuit 26, and a waveform detectioncircuit 28.

The power reception device 40 includes a power reception section 40, aload modulation section 46, and a power supply control section 48. Theload (battery device) 90 includes the charge control device 92 and thebattery (secondary battery) 94. The details are described below.

A power-transmission-side electronic instrument such as the charger 500includes at least the power transmission device 10 shown in FIG. 2. Apower-reception-side electronic instrument such as the portabletelephone 510 includes at least the power reception device 40 and thebattery device 90.

The configuration shown in FIG. 2 implements a non-contact powertransmission (contactless power transmission) system in which power istransmitted from the power transmission device 10 to the power receptiondevice 40 by electromagnetically coupling the primary coil L1 and thesecondary coil L2, and power (voltage VOUT) is supplied to the batterydevice 90 from a voltage output node NB7 of the power reception device40.

The power transmission device 10 (power transmission module or primarymodule) may include the primary coil L1, the power transmission section12, the waveform monitoring circuit 14, a display section 16, and thepower transmission control device 20. The power transmission device 10and the power transmission control device 20 are not limited to theconfiguration shown in FIG. 2. Various modifications may be made such asomitting some elements (e.g., display section and waveform monitoringcircuit), adding other elements, or changing the connectionrelationship.

The power transmission section 12 generates an alternating-currentvoltage at a given frequency during power transmission, and generates analternating-current voltage at a frequency which differs depending ondata during data transfer. The power transmission section 12 suppliesthe generated alternating-current voltage to the primary coil L1.

FIGS. 4A and 4B are views illustrative of the principle of informationtransmission between a primary-side instrument and a secondary-sideinstrument.

Information is transmitted from the primary-side instrument to thesecondary-side instrument utilizing frequency modulation. Information istransmitted from the secondary-side instrument to the primary-sideinstrument utilizing load modulation.

As shown in FIG. 4A, the power transmission device 10 generates analternating-current voltage at a frequency f1 when transmitting data “1”to the power reception device 40, and generates an alternating-currentvoltage at a frequency f2 when transmitting data “0” to the powerreception device 40, for example. As shown in FIG. 4B, the powerreception device 40 can switch the load state between a low-load stateand a high-load state by load modulation to transmit data “0” or “1” tothe primary-side instrument (power transmission device 10).

The power transmission section 12 shown in FIG. 3 may include a firstpower transmission driver that drives one end of the primary coil L1, asecond power transmission driver that drives the other end of theprimary coil L1, and at least one capacitor that forms a resonantcircuit with the primary coil L1. Each of the first and second powertransmission drivers included in the power transmission section 12 is aninverter circuit (or buffer circuit) that includes a power MOStransistor, for example, and is controlled by the driver control circuit26 of the power transmission control device 20.

The primary coil L1 (power-transmission-side coil) iselectromagnetically coupled with the secondary coil L2(power-reception-side coil) to form a power transmission transformer.For example, when power transmission is necessary, the portabletelephone 510 is placed on the charger 500 so that a magnetic flux ofthe primary coil L1 passes through the secondary coil L2, as shown inFIG. 1. When power transmission is unnecessary, the charger 500 and theportable telephone 510 are physically separated so that a magnetic fluxof the primary coil L1 does not pass through the secondary coil L2.

As the primary coil L1 and the secondary coil L2, a planar coil formedby spirally winding an insulated wire in a single plane may be used, forexample. Note that a planar coil formed by spirally winding a twistedwire (i.e., a wire obtained by twisting a plurality of insulated thinwires) may also be used.

The waveform monitoring circuit 14 is a circuit that detects an inducedvoltage in the primary coil L1. The waveform monitoring circuit 14includes resistors RA1 and RA2, and a diode DA1 provided between aconnection node NA3 of the resistors RA1 and RA2 and a power supply GND(low-potential-side power supply in a broad sense), for example.Specifically, a signal PHIN obtained by dividing the induced voltage inthe primary coil L1 using the resistors RA1 and RA2 is input to thewaveform detection circuit 28 of the power transmission control device20.

The display section 16 displays the state (e.g., power transmission orID authentication) of the non-contact power transmission system using acolor, an image, or the like. The display section 16 is implemented by alight-emitting diode (LED), a liquid crystal display (LCD), or the like.

The power transmission control device 20 controls the power transmissiondevice 10. The power transmission control device 20 may be implementedby an integrated circuit device (IC) or the like. The power transmissioncontrol device 20 includes the power-transmission-side control circuit22, the oscillation circuit 24, the driver control circuit 26, and thewaveform detection circuit 28.

The power-transmission-side control circuit 22 controls the powertransmission device 10 and the power transmission control device 20. Thepower-transmission-side control circuit 22 may be implemented by a gatearray, a microcomputer, or the like.

Specifically, the power-transmission-side control circuit 22 performssequence control and a determination process necessary for powertransmission, load detection, frequency modulation, foreign objectdetection, removal (detachment) detection, and the like. Thepower-transmission-side control circuit 22 starts temporary powertransmission for position detection and ID authentication targeted atthe power reception device 40 when the switch (SW) has been turned ON,for example.

The oscillation circuit 24 includes a crystal oscillation circuit or thelike, and generates a primary-side clock signal. The driver controlcircuit 26 generates a control signal at a desired frequency based onthe clock signal generated by the oscillation circuit 24, a frequencysetting signal output from the control circuit 22, and the like, andoutputs the generated control signal to the power transmission drivers(not shown) of the power transmission section 12 to control theoperations of the power transmission drivers.

The waveform detection circuit 28 monitors the waveform of the signalPHIN that corresponds to an induced voltage at one end of the primarycoil L1, and performs load detection, foreign object detection, and thelike. For example, when the load modulation section 46 of the powerreception device 40 has performed load modulation for transmitting datato the power transmission device 10, the signal waveform of the inducedvoltage in the primary coil L1 changes correspondingly.

As shown in FIG. 4B, the amplitude (peak voltage) of the signal waveformdecreases when the load modulation section 46 of the power receptiondevice 40 reduces load in order to transmit data “0”, and the amplitudeof the signal waveform increases when the load modulation section 46increases load in order to transmit data “1”. Therefore, the waveformdetection circuit 28 can determine whether the data transmitted from thepower reception device 40 is “0” or “1” by determining whether or notthe peak voltage has exceeded a threshold voltage, by performing apeak-hold process on the signal waveform of the induced voltage, forexample. Note that the waveform detection method is not limited to theabove-described method. For example, the amplitude detection circuit 28may determine whether the power-reception-side load has increased ordecreased using a physical quantity (e.g., the phase difference ofcurrent or voltage or the width of a pulse generated based on a voltagewaveform) other than the peak voltage.

The power reception device 40 (power reception module or secondarymodule) may include the secondary coil L2, the power reception section42, the load modulation section 46, the power supply control section 48,and a power reception control device 50. Note that the power receptiondevice 40 and the power reception control device 50 are not limited tothe configuration shown in FIG. 3. Various modifications may be madesuch as omitting some elements, adding other elements, or changing theconnection relationship.

The power reception section 42 converts an alternating-current inducedvoltage in the secondary coil L2 into a direct-current voltage. Arectifier circuit 43 included in the power reception section 42 convertsthe alternating-current induced voltage. The rectifier circuit 43includes diodes DB1 to DB4. The diode DB1 is provided between a node NB1at one end of the secondary coil L2 and a node NB3 (direct-currentvoltage VDC generation node). The diode DB2 is provided between the nodeNB3 and a node NB2 at the other end of the secondary coil L2. The diodeDB3 is provided between the node NB2 and a node NB4 (VSS). The diode DB4is provided between the nodes NB4 and NB1.

Resistors RB1 and RB2 of the power reception section 42 are providedbetween the nodes NB1 and NB4. A signal CCMPI obtained by dividing thevoltage between the nodes NB1 and NB4 using the resistors RB1 and RB2 isinput to a frequency detection circuit 60 of the power reception controldevice 50.

A capacitor CB1 and resistors RB4 and RB5 of the power reception section42 are provided between the node NB3 (direct-current voltage VDC) andthe node NB4 (VSS). A signal VD4 obtained by dividing the voltagebetween the nodes NB3 and NB4 using the resistors RB4 and RB5 is inputto a power-reception-side control circuit 52 and a position detectioncircuit 56 through a signal line LP2. The divided voltage VD4 is inputto the position detection circuit 56 as a frequency detection signalinput (ADIN).

The load modulation section 46 performs a load modulation process.Specifically, when the power reception device 40 transmits desired datato the power transmission device 10, the load modulation section 46variably changes the load of the load modulation section 46 (secondaryside) depending on the transmission target data to change the signalwaveform of the induced voltage in the primary coil L1. The loadmodulation section 46 includes a resistor RB3 and a transistor QB3(N-type CMOS transistor) provided in series between the nodes NB3 andNB4.

The transistor QB3 (load-modulation transistor) is ON/OFF-controlledbased on a control signal P3Q supplied from the power-reception-sidecontrol circuit 52 of the power reception control device 50 through asignal line LP3. When performing the load modulation process byON/OFF-controlling the transistor QB3 and transmitting a signal to thepower transmission device in an authentication stage before normal powertransmission starts, transistor QB2 of the power supply control section48 is turned OFF so that the battery device 90 is not electricallyconnected to the power reception device 40.

For example, when reducing the secondary-side load (high impedance) inorder to transmit data “0”, the signal P3Q is set at the L level so thatthe transistor QB3 is turned OFF. As a result, the load of the loadmodulation section 46 becomes almost infinite (no load). On the otherhand, when increasing the secondary-side load (low impedance) in orderto transmit data “1”, the signal P3Q is set at the H level so that thetransistor QB3 is turned ON. As a result, the load of the loadmodulation section 46 (i.e., the load of the power reception device 40)is equivalent to the resistor RB3 (high load).

The power supply control section 48 controls power supplied to thebattery device 90. A regulator (LDO) 49 regulates the voltage level ofthe direct-current voltage VDC obtained by conversion by the rectifiercircuit 43 to generate a power supply voltage VD5 (e.g., 5 V). The powerreception control device 50 operates based on the power supply voltageVD5 supplied from the power supply control section 48, for example.

A switch circuit formed using a PMOS transistor (M1) is provided betweenthe input terminal and the output terminal of the regulator (LDO) 49. Apath that bypasses the regulator (LDO) 49 is formed by causing the PMOStransistor (M1) as the switch circuit to be turned ON. For example,since a power loss increases due to the equivalent impedance of theregulator 49 and heat generation increases under heavy load (e.g., whenit is necessary to cause an almost constant large current to steadilyflow in the initial stage of charging a secondary battery which has beenexhausted to a large extent), a current is supplied to the load througha path that bypasses the regulator.

An NMOS transistor (M2) and a pull-up resistor R8 that function as abypass control circuit are provided to ON/OFF-control the PMOStransistor (M1) as the switch circuit.

The NMOS transistor (M2) is turned ON when a high-level control signalis supplied to the gate of the NMOS transistor (M2) through a signalline LP4. This causes the gate of the PMOS transistor (M1) to be set ata low level so that the PMOS transistor (M1) is turned ON, whereby apath that bypasses the regulator (LDO) 49 is formed. When the NMOStransistor (M2) is turned OFF, the gate of the PMOS transistor (M1) ismaintained at a high level through the pull-up resistor R8. Therefore,the PMOS transistor (M1) is turned OFF so that the bypass path is notformed.

The NMOS transistor (M2) is ON/OFF-controlled by the power receptioncontrol circuit 52 included in the power reception control device 50.

A transistor QB2 (P-type CMOS transistor) is provided between a powersupply voltage (VD5) generation node NB5 (output node of the regulator49) and a node NB6, and is controlled based on a signal P1Q from thecontrol circuit 52 of the power reception control device 50.Specifically, the transistor QB2 is turned ON when ID authentication hasbeen completed (established) and normal power transmission is performed.

A pull-up resistor RU2 is provided between the power supply voltagegeneration node NB5 and a node NB8 of the gate of the transistor QB2.

The power reception control device 50 controls the power receptiondevice 40. The power reception control device 50 may be implemented byan integrated circuit device (IC) or the like. The power receptioncontrol device 50 may operate based on the power supply voltage VD5generated based on the induced voltage in the secondary coil L2. Thepower reception control device 50 may include the (power-reception-side)control circuit 52, the position detection circuit 56, an oscillationcircuit 58, the frequency detection circuit 60, and a full-chargedetection circuit 62.

The power-reception-side control circuit 52 controls the power receptiondevice 40 and the power reception control device 50. The power receptioncontrol circuit 52 may be implemented by a gate array, a microcomputer,or the like. The power-reception-side control circuit 52 operates basedon a constant voltage (VD5) at the output terminal of the seriesregulator (LDO) 49 as a power supply voltage. The power supply voltage(VD5) is supplied to the power-reception-side control circuit 52 througha power supply line LP1.

The power-reception-side control circuit 52 performs sequence controland a determination process necessary for ID authentication, positiondetection, frequency detection, full-charge detection, load modulationfor authentication communication, load modulation for communication thatenables detection of foreign object insertion, and the like.

The position detection circuit 56 monitors the waveform of the signalADIN that corresponds to the waveform of the induced voltage in thesecondary coil L2, and determines whether or not the positionalrelationship between the primary coil L1 and the secondary coil L2 isappropriate.

Specifically, the position detection circuit 56 converts the signal ADINinto a binary value using a comparator, and determines whether or notthe positional relationship between the primary coil L1 and thesecondary coil L2 is appropriate.

The oscillation circuit 58 includes a CR oscillation circuit or thelike, and generates a secondary-side clock signal. The frequencydetection circuit 60 detects the frequency (f1 or f2) of the signalCCMPI, and determines whether the data transmitted from the powertransmission device 10 is “1” or “0”.

The full-charge detection circuit 62 (charge detection circuit) detectswhether or not the battery 94 of the battery device 90 has been fullycharged (charged). Specifically, the full-charge detection circuit 62detects the full-charge state by detecting whether a light-emittingdevice LED used to indicate the charge state is turned ON or OFF, forexample. The full-charge detection circuit 62 determines that thebattery 94 has been fully charged (charging has been completed) when thelight-emitting device LED has been turned OFF for a given period of time(e.g., five seconds).

The charge control device 92 provided in the battery device 90 alsodetects the full-charge state based on the ON/OFF state of thelight-emitting device LED.

The battery device 90 includes the charge control device 92 thatcontrols charging of the battery 94 and the like. The charge controldevice 92 detects the full-charge state based on the ON/OFF state of thelight-emitting device (LED). The charge control device 92 (chargecontrol IC) may be implemented by an integrated circuit device or thelike. The battery 94 may be provided with the function of the chargecontrol device 92. In this case, the battery 94 corresponds to thebattery device (load device) 90 in this specification.

The power reception device 40 includes four terminals (TA1 to TA4), asdescribed above with reference to FIG. 2. The battery device 90 alsoincludes four terminals (TA5 to TA8). The power reception control device50 includes two terminals (i.e., ICUTX signal output terminal TA3 andLEDR signal input terminal TA4).

Note that the battery device 90 is not limited to a secondary battery.For example, a given circuit may serve as a load when the circuitoperates. The details of takeover state detection (measures againsttakeover heat generation) are described below.

Measures Against Takeover Heat Generation

A large foreign object may be inserted between the primary coil and thesecondary coil after the instrument has been authenticated and normalpower transmission has started. A small or medium-sized metal foreignobject can be detected by monitoring the induced voltage in the primarycoil (L1).

However, when a metal foreign object (e.g., thin metal sheet) thatblocks the primary coil and the secondary coil has been inserted betweenthe primary-side instrument and the secondary-side instrument (see FIGS.5A and 5B), the energy transmitted from the primary-side instrument isconsumed by the metal foreign object (i.e., the metal foreign objectacts as a load). Therefore, the primary-side instrument regards themetal foreign object as the battery (secondary-side instrument).

Accordingly, a situation in which removal of the secondary-sideinstrument cannot be detected based on the induced voltage in theprimary coil may occur, for example. In this case, power transmissionfrom the primary-side instrument is continuously performed although thesecondary-side instrument is absent, whereby the temperature of themetal foreign object increases to a large extent.

A phenomenon in which a metal foreign object takes over thesecondary-side instrument in this way is hereinafter referred to as“takeover (phenomenon)”. A phenomenon in which heat is generated due tothe takeover state is hereinafter referred to as “takeover heatgeneration”.

In order to improve the safety and the reliability of the non-contactpower transmission system to a practical level, it is necessary to takesufficient measures against such takeover heat generation.

A foreign object may be inserted accidentally or intentionally. When aforeign object has been inserted, a skin burn or damage to ordestruction of the instrument may occur due to heat generation.Therefore, sufficient safety measures against foreign object insertionmust be taken for the non-contact power transmission system. Measuresagainst takeover heat generation are described in detail below.

FIGS. 5A and 5B are cross-sectional views showing electronic instrumentsthat form a non-contact power transmission system which are illustrativeof insertion of a foreign object (takeover state) after normal powertransmission has started.

In FIG. 5A, the portable telephone 510 (electronic instrument includingthe power reception device 40) is placed at a given position on thecradle 500 (electronic instrument including the power transmissiondevice 10). Non-contact power transmission is performed from the cradle500 (charger) to the portable telephone 510 through the primary coil andthe secondary coil so that the secondary battery (e.g., battery pack)provided in the portable telephone 510 is charged.

In FIG. 5B, a thin sheet-shaped metal foreign object (conductive foreignobject) AR is intentionally inserted between the cradle 500 (charger)and the portable telephone 510 during normal power transmission. Whenthe foreign object AR has been inserted, power supplied from theprimary-side instrument (cradle 500) to the secondary-side instrument(portable telephone terminal 510) is almost entirely consumed by theforeign object (AR) (i.e., the transmitted power is taken over), wherebythe foreign object AR is likely to generate heat. When the state shownin FIG. 5B has occurred, the power transmission device 10 included inthe primary-side instrument (cradle 500) must detect insertion of theforeign object AR and immediately stop normal power transmission.

However, it is difficult to detect the takeover state shown in FIG. 5Busing a metal foreign object detection method based on the inducedvoltage in the primary coil (L1).

For example, the amplitude of the voltage induced in the primary coil(L1) increases as the load of the power reception device increases, anddecreases as the load of the power reception device decreases. If thesecondary battery of the portable telephone 510 is normally charged, theload of the power reception device 40 gradually decreases with thepassage of time. When the load of the power reception device 40 hasrapidly increased, the power transmission device 10 can detect the rapidincrease in load since the power transmission device 10 monitors achange in the load of the power reception device 40. However, the powertransmission device 10 cannot determine whether the increase in load hasoccurred due to the battery (the secondary battery of the portabletelephone), mispositioning between the portable telephone 510 and thecradle 500, or insertion of a foreign object. Therefore, insertion of aforeign object cannot be detected using the method in which the powertransmission device 10 merely detects a change in the load of the powerreception device 40.

In this embodiment, the power reception device 40 intermittently changesthe load of the power reception device 40 during normal powertransmission while supplying power to the battery (e.g., secondarybattery) (regular load modulation operation) to transmit information tothe power transmission device 10.

The following items are confirmed when the power transmission device 10has detected the information due to an intermittent change in load at agiven timing.

(1) The instrument (i.e., portable telephone 510) including the powerreception device 40 is appropriately placed on the instrument (i.e.,cradle 500) including the power transmission device 10.

(2) The instrument (including the secondary battery of the portabletelephone 510) including the power reception device 40 is operatingnormally.

(3) The foreign object AR is not inserted.

When the foreign object AR has been inserted during normal powertransmission, the information transmitted from the power receptiondevice 40 is blocked by the foreign object AR and does not reach thepower transmission device 10. Specifically, the power transmissiondevice 10 cannot detect an intermittent (e.g., regular) change in theload of the power reception device. It is most likely that anintermittent change in load cannot be detected after the above-mentioneditems (1) to (3) have been confirmed because the foreign object AR hasbeen inserted (item (3)). Specifically, the power transmission device 10can determine that the power transmission device 10 has become unable todetect an intermittent change in load due to insertion of the foreignobject AR.

FIGS. 6A and 6B are views illustrative of a specific embodiment whenintermittently changing the load of the power reception device so thatinsertion of a foreign object can be detected.

In FIG. 6A, an intermittent change in the load of the power receptiondevice is indicated by a change in secondary current (current that flowsthrough the secondary coil L2). As shown in FIG. 6A, the load of thepower reception device intermittently changes at times t1, t2, t3, t4,t5,

In FIG. 6A, the load changes in a cycle T3. The load decreases in aperiod T2 starting from the time t1, and increases in the subsequentperiod T1, for example. Such a cyclic change in load is repeated in thecycle T3.

FIG. 6B shows a change in primary coil voltage (induced voltage at oneend of the primary coil) with respect to a change in secondary loadcurrent. The secondary-side load increases in the period T1, anddecreases in the period T2, as described above. The amplitude (peakvalue) of the induced voltage (primary coil voltage) at one end of theprimary coil (L1) changes corresponding to the change in secondary-sideload. Specifically, the amplitude increases in the period T1 in whichthe load increases, and decreases in the period T2 in which the loaddecreases. Therefore, the power transmission device 10 can detect achange in the load of the power reception device 40 by detecting thepeak of the primary coil voltage using the waveform monitoring circuit14 (see FIG. 3), for example. Note that the load change detection methodis not limited to the above-described method. For example, the phase ofthe primary coil voltage or the primary coil current may be detected.

The load can be easily modulated by switching the transistor, forexample. The peak voltage of the primary coil or the like can beaccurately detected using an analog or digital basic circuit. Therefore,the above method does not impose load on the instrument to a largeextent while facilitating implementation. The above-described method isalso advantageous in terms of a reduction in mounting area and cost.

As described above, insertion of a foreign object can be easily andaccurately detected without adding a special configuration by employinga novel method in which the power reception device 40 transmitsinformation obtained by intermittently (and cyclically) changing theload during normal power transmission and the power transmission device10 detects the change in load.

Specific Example of Detection of Foreign Object Insertion

FIG. 7 is a circuit diagram showing the configuration of the non-contactpower transmission system shown in FIG. 2 relating to detection offoreign object insertion (takeover state). In FIG. 7, the same sectionsas in FIG. 2 are indicated by the same reference symbols. In FIG. 7, abold line indicates a portion that plays an important role in detectinginsertion of a foreign object.

A notable circuit configuration of the power reception device 40 shownin FIG. 7 includes the load-modulation transistor QB3 of the loadmodulation section 46, the power supply control transistor QB2 of thepower supply control section 48, and the power reception control circuit52 that ON/OFF-controls these transistors (QB2 and QB3). The voltages atthe input terminal and the output terminal of the series regulator (LDO)49 are input to the power-reception-side control circuit 52 through thesignal lines LP2 and LP1 so that the load state (degree of load) of thebattery (secondary battery) 94 included in the battery device 90 can bedetected by monitoring the voltage across the series regulator (LDO) 49.

The power transmission device 10 detects the peak value (amplitude) ofthe induced voltage in the primary coil (L1) using the waveformdetection circuit 28, and detects a change in the load of the powerreception device 40 using the power-transmission-side control circuit22.

In FIG. 7, the power reception device 40 modulates the load duringnormal power transmission (continuous power transmission afterauthentication), and transmits a foreign object detection pattern PT1 tothe power transmission device 10. The power-transmission-side controlcircuit 22 of the power transmission device 10 (successively orintermittently) monitors a change in the load of the power receptiondevice 40 during normal power transmission. The power-transmission-sidecontrol circuit 22 determines that the foreign object AR has beeninserted when the power-transmission-side control circuit 22 has becomeunable to receive the foreign object detection pattern PT1, and stopsnormal power transmission.

Specific Embodiment of Foreign Object Detection Pattern PT1

FIGS. 8A and 8B are views illustrative of a preferred and specific modeof load modulation which enables detection of a foreign object. FIG. 8Ais a view showing a timing example of load modulation, and FIG. 8B is aview showing a change in the load of the power reception device detectedby the power transmission device in detail.

As shown in FIG. 8A, load modulation that enables foreign objectdetection is cyclically (regularly) performed in a cycle of 10 sec, forexample.

Load modulation that enables foreign object detection is performed in aperiod from time t1 to t6 and a period from time t7 to t12. The periodfrom time t1 to t6 (from time t7 to t12) is 0.5 sec. The degree of loadis changed in units of 0.1 sec (100 msec) obtained by equally dividing0.5 sec by five.

In FIG. 8A, a bold bidirectional line indicates a period in which theload increases. Specifically, the load increases in a period from timet1 to t2, a period from time t3 to t4, a period from time t5 to t6, aperiod from time t7 to t8, a period from time t9 to t10, and a periodfrom time t11 to t12. A period in which the load increases is referredto as a period TA.

The load decreases in a period from time t2 to t3, a period from time t4to t5, a period from time t8 to t9, and a period from time t10 to t11. Aperiod in which the load decreases is referred to as a period TB.

In FIG. 8A, the load of the power reception device is intermittentlychanged cyclically (i.e., in cycle units (in units of one cycle)) duringnormal power transmission, and the load is intermittently changed aplurality of times at given intervals within one cycle.

The power transmission device 10 and the power reception device 40 cantransfer the information relating to a change in load in synchronizationby cyclically changing the load (i.e., the power transmission device 10can easily determine the timing at which the load of the power receptiondevice 40 changes).

The power transmission device 10 can easily determine whether a changein load is noise or a normal signal when detecting a change in load byintermittently changing the load a plurality of times at given intervalswithin one cycle, whereby the foreign object detection accuracy can beincreased. Specifically, when the load changes only once within onecycle, it may be difficult to determine whether a change in load withrespect to the power transmission device 10 occurs accidentally or dueto load modulation. On the other hand, when the load changes a pluralityof times within one cycle, it is easy to determine that the change inload has occurred due to load modulation.

In FIG. 8A, the load is intermittently changed a plurality of times atgiven intervals only in a given period (times t1 to t6) within one cycle(e.g., times t1 to t7). Specifically, load modulation is performed onlyin the first period (0.5 sec) of one cycle (10 sec). The reasons thatload modulation is performed in this manner are as follows.

Specifically, since a change in load (load modulation) during normalpower transmission may affect power supply to the battery 94, it isundesirable to frequently change the load to a large extent. Therefore,one cycle of load modulation is increased to some extent (a foreignobject can be detected even if the cycle of load modulation is increasedto some extent).

The load is intermittently changed a plurality of times at givenintervals only in a given period within one cycle. Specifically, whenthe load change interval is increased to a large extent, the powertransmission device may not appropriately detect an intermittent changein the load of the power reception device due to a change in the loadstate of the battery with the passage of time or a change in surroundingconditions. Therefore, one cycle is increased (10 sec in FIG. 8A), andthe load is intermittently modulated a plurality of times (five times inFIG. 8A) only in a short period (0.5 sec in FIG. 8A) within one cycle,for example.

The power transmission device 10 can detect a foreign object (AR) withhigh accuracy while minimizing an effect on power supply to the battery(power-supply-target load) 94 (e.g., charging of a battery pack) byperforming load modulation in this manner.

FIG. 8B shows an example of a change in the amplitude of the inducedvoltage at one end of the primary coil (L1) of the power transmissiondevice 10 corresponding to the load of the power reception device. InFIG. 8B, the load state of the battery 94 differs between a loadmodulation period (t1 to t6) in the first cycle and a load modulationperiod (t7 to t12) in the second cycle. The load state of the battery 94increases in the second cycle so that the peak value of the primary coilvoltage increases.

At times t1 to t6 in FIG. 8B, the difference between the primary coilvoltage in the period TA in which the load increases and the primarycoil voltage in the period TB in which the load decreases is ΔV1. Thepower-transmission-side control circuit 22 of the power transmissiondevice 10 can detect a change in the load of the power reception device40 from the difference ΔV1 in the amplitude of the primary coil voltage.

In the second load modulation period (times t7 to t12), since the loadstate of the battery 94 increases so that a charging current (Iload)supplied to the battery 94 increases, the ratio of a modulation current(Imod) due to load modulation to the charging current (Iload) decreasesso that the difference in primary coil voltage caused by causing themodulation current (Imod) to be turned ON/OFF decreases to ΔV2(ΔV2<ΔV1). Specifically, the modulation current (Imod) is buried in thecharging current (Iload) supplied to the battery 94. Therefore, when theload state of the battery 94 is heavy, it is difficult for the powertransmission device 10 to detect a change in load as compared with thecase where the load state of the battery 94 is light.

In this embodiment, the load state of the battery 94 is reduced byreducing power supplied to the battery 94 so that the primary-sideinstrument can easily detect a change in load due to load modulation.The battery load reduction measures are described below.

Process of Reducing Load State of Battery

In the invention, since load modulation is performed while transmittingpower to the battery 94 during normal power transmission, transmissionof a signal due to load modulation to the power transmission device 10is necessarily affected by the state of power supply to the battery 94(i.e., the load state of the battery).

As described above, even if a small current is turned ON/OFF for loadmodulation when a large amount of charging current is supplied to thebattery 94 (e.g., battery pack), since the amount of ON/OFF current(Imod) is smaller than the amount of charging current (Iload) suppliedto the battery 94, it is difficult for the power transmission device 10to detect a change in load due to load modulation (i.e., it is difficultfor the power transmission device 10 to detect whether a change in loadis noise or a signal due to load modulation). On the other hand, therelative ratio of the ON/OFF current (Imod) due to load modulationincreases when the amount of current supplied to the load 94 is small(when the load of the battery is light), so that the power transmissiondevice 10 can easily detect a change in load due to the ON/OFFoperation.

Therefore, the power reception device 40 monitors the load state of thebattery 94 during normal power transmission, and reduces the amount ofpower supplied to the battery 94 when the load state of the battery 94is heavy (i.e., a large amount of current is supplied to the battery 94)when the power reception device 40 performs load modulation that enablesforeign object detection.

Since the load state of the battery 94 is apparently reduced by reducingthe amount of power supplied to the battery 94, the power transmissiondevice 10 can easily detect a signal due to load modulation. Therefore,the foreign object detection accuracy is maintained at a desired leveleven when the load state of the battery 94 is heavy. Since at least aminimum amount of power is always supplied to the battery 94 even whencompulsorily reducing the load state of the battery 94, a problem inwhich the electronic circuit (charge control device 92) of the battery94 cannot operate does not occur.

Moreover, since load modulation that enables detection of foreign objectinsertion is intermittently performed at appropriate intervals takingthe effect on power supply to the battery 94 into consideration, powersupply to the battery 94 is not adversely affected even if the load isreduced. For example, a problem in which the charging time of thebattery pack increases to a large extent does not occur.

Therefore, the load change detection accuracy of the power transmissiondevice 10 can be maintained at a desired level, even if the load stateof the battery 94 is heavy, by causing the power reception device 40 tomonitor the state of the battery 94 and optionally reduce the load stateof the battery 94 when performing load modulation that enables detectionof foreign object insertion.

Note that the load reduction process may be uniformly performedregardless of the load state of the battery 94. This makes itunnecessary to monitor the load state of the battery so that loadimposed on the power-reception-side control circuit 52 is reduced.

FIGS. 9A to 9E are views illustrative of the battery load reductionoperation. FIG. 9A is a view showing a state in which the load state ofthe battery is light. FIG. 9B is a view showing a state in which theload state of the battery is heavy. FIG. 9C is a view showing a changein primary coil voltage in the state shown in FIG. 9B. FIG. 9D is a viewshowing a state in which the load state of the battery is reduced bycausing the power supply control transistor to be turned ON/OFF orsetting the power supply control transistor in a half ON state. FIG. 9Eis a view showing a change in primary coil voltage in the state shown inFIG. 9D.

In FIG. 9A, since the load state of the battery 94 is light (i.e., thecharging current Iload supplied to the battery is small), the powertransmission device 10 can sufficiently detect a change in load due toload modulation without causing the power reception device 40 to reducethe load state of the battery. Therefore, the power supply controltransistor QB2 is always turned ON. The load modulation transistor QB3is intermittently turned ON/OFF to implement load modulation.

In FIG. 9B, since the load state of the battery 94 is heavy (i.e., thecharging current Iload supplied to the battery is large), a change inmodulation current (Imod) due to the ON/OFF operation is observed toonly a small extent. As shown in FIG. 9C, when the load state of thebattery has increased, the difference in amplitude of the primary coilvoltage decreases from ΔV1 to ΔV2, whereby it becomes difficult todetect a change in load due to load modulation.

In FIG. 9D, the power reception device 40 reduces the load state of thebattery when performing load modulation. In FIG. 9D, the power receptiondevice 40 causes the power supply control transistor QB2 to besuccessively turned ON/OFF or sets the power supply control transistorQB2 in a half ON state.

Specifically, the amount of power supplied to the battery 94 can bereduced by utilizing a digital method in which the power receptiondevice 40 causes the power supply control transistor QB2 provided in apower supply path to be successively turned ON/OFF to intermittentlysupply power to the battery 94. An operation of successively switching atransistor is generally employed for a digital circuit, and is easilyimplemented. Moreover, it is possible to accurately reduce the amount ofpower supplied to the battery by selecting the switching frequency.

The amount of power supplied to the battery 94 can also be reduced byutilizing an analog method in which an intermediate voltage between acomplete ON voltage and a complete OFF voltage is supplied to the gateof the power supply control transistor (PMOS transistor) to set the PMOStransistor in a half ON state. This method has an advantage in that theon-resistance of the power supply control transistor (PMOS transistor)can be finely adjusted by controlling the gate voltage.

In FIG. 9E, the amplitude of the primary coil voltage in a state inwhich the load state of the battery is heavy changes from V10 to V20 bycompulsorily reducing the load state of the battery. In FIG. 9E, “X”indicates the amount by which the load state of the battery 94 isreduced. The difference in amplitude of the primary coil voltageincreases from ΔV2 (see FIG. 9C) to ΔV3 (ΔV3>ΔV2) by compulsorilyreducing the load state of the battery 94, whereby the powertransmission device 10 can easily detect a change in the load of thepower reception device 40 due to load modulation.

The power transmission device can reliably detect a change in load, evenwhen the load state of the battery is heavy, by causing the powerreception device to reduce the load state of the battery whileperforming load modulation.

Load modulation timing and load reduction timing

FIGS. 10A and 10B are views illustrative of the load modulation timingand the load reduction timing.

As shown in FIG. 10A, the power-reception-side control circuit 52provided in the power reception control device 50 causes the loadmodulation section 46 provided in the power reception device 40 toperform load modulation using a load modulation signal (LP3) whilereducing the load state of the battery 94 by controlling the operationof the charge control device 92 using the power supply control signal(ICUTX).

As shown in FIG. 10B, intermittent load modulation is regularly(cyclically) performed in a cycle TX. The power control signal (ICUTX)is set at the low level in a first period (t20 to t23 and t24 to t27) ofthe load modulation period TX. Therefore, the operation of the chargecontrol device 92 is compulsorily controlled so that the chargingcurrent supplied to the battery 94 is reduced or temporarily stopped.

When reducing the charging current (i.e., the charging current is notturned OFF), an increase in charging time can be minimized since thebattery 94 is continuously charged. Moreover, since a CPU provided inthe charge control device 92 is not reset, the normal operation of thecharge control device 92 can be maintained.

When temporarily stopping the charging current, the charging timeincreases to some extent since charging of the battery is temporarilystopped. On the other hand, since the effect of battery charging on theload modulation signal is completely eliminated, the power transmissiondevice 10 (primary-side instrument) can more easily detect a change inload.

It is desirable to supply a minimum amount of power that enables the CPUto operate during load reduction instead of completely stopping powersupply, taking into account the charging time and the effect ofpreventing the CPU provided in the charge control device 92 from beingreset (note that the invention is not limited thereto).

The first period (t20 to t23 and t24 to t27) of the load modulationperiod may be referred to as a load reduction period. The second period(t23 to t24 and t27 to t28) is referred to as a normal operation period.

As shown in FIG. 10B, the load modulation signal LP3 is activated in anintermediate period (t21 to t22 and t25 to t26) of the load reductionperiod so that load reduction is performed. When the load-modulationtransistor QB3 shown in FIG. 7 is turned ON, the modulation current(Imod) flows so that the load with respect to the primary-sideinstrument (i.e., the load of the secondary-side instrument) increasesapparently. When the load-modulation transistor QB3 is turned OFF, thelow-load (or no-load) state is recovered.

Specifically, the load with respect to the primary-side instrument(i.e., the load of the secondary-side instrument) changes in the orderof “light”, “heavy”, and “light”. The primary-side instrument detectssuch a specific change in load. The primary-side instrument determinesthat a takeover state due to a foreign object insertion has occurredwhen the primary-side instrument cannot detect a regular change in load,and stops power transmission. The primary-side instrument can easilydetect a change in load by reducing the load.

Internal Configuration and Operation of Charge Control Device

A specific embodiment when controlling battery charging using the powersupply control signal (ICUTX) is described below with reference to FIGS.11 to 14. An example that adjusts a current regulation resistor, anexample that utilizes negative feedback control, and an example thatdirectly controls power supply through a power supply path, are givenbelow in that order.

(1) Example that Adjusts Current Regulation Resistor (e.g., ExternalResistor) Using Signal ICUTX

FIGS. 11A and 11B are views illustrative of an example of battery chargecontrol (example that uses a current regulation resistor). FIG. 11Ashows a connection state of a charger (charge control IC) 91, currentregulation resistors (R19 and R17), and the like included in the chargecontrol device 92. FIG. 11B shows the charging characteristics of thebattery 94 (e.g., lithium-ion battery).

As shown in FIG. 11A, the charger (charge control IC) 91 includes sixterminals. A first terminal is a power supply terminal that receives avoltage (Vin) supplied from the power reception device 40.

A second terminal is a terminal for detecting the charge state of thebattery 94. A third terminal is a terminal that receives an enablesignal (EN).

A fourth terminal is a terminal for charging the battery 94. A fifthterminal is a terminal connected to the external current regulationresistors (R19 and R17). Note that the current regulation resistors (R19and R17) may be provided in the charger (charge control IC) 91. A sixthterminal is a ground terminal.

The current regulation resistor (external resistor) R19 is connectedbetween the fifth terminal of the charger (charge control IC) 91 andground. The current regulation resistor (external resistor) R17 and anNMOS transistor (M15) as a control element (charging current controlelement) are connected in series between the fifth terminal of thecharger (charge control IC) 91 and ground.

The NMOS transistor (M15) as the control element (charging currentcontrol element) functions as a switching element, for example. The gateof the NMOS transistor (M15) is driven using the power supply controlsignal (ICUTX) so that the NMOS transistor (M15) is turned ON/OFF.

When the NMOS transistor (M15) is turned ON, the current regulationresistors (R19 and R17) are connected in parallel between the fifthterminal and ground. The resistance of a combined resistor formed by thecurrent regulation resistors (R19 and R17) connected in parallel issmaller than the resistance of the current regulation resistor R19.

When the NMOS transistor (M15) is turned OFF, the current regulationresistor R17 is disabled (i.e., only the current regulation resistor R19is enabled).

The charging current supplied to the battery 94 decreases as theresistance of the current regulation resistors (R19 and R17) increases,and increases as the resistance of the current regulation resistors (R19and R17) decreases. Specifically, the current regulation resistors (R19and R17) have a function of adjusting the amount of reference current ofa current mirror that determines the charging current supplied to thebattery, for example. The reference current decreases as the resistanceof the current regulation resistors (R19 and R17) increases so that thecharging current (Iload) supplied to the battery is compulsorily reduced(i.e., the amount of power supplied is limited).

The NMOS transistor (M15) is turned ON when the power supply controlsignal (ICUTX) is inactive (H level), so that the current regulationresistors (R19 and

R17) are connected in parallel between the fifth terminal and ground.The NMOS transistor (M15) is turned OFF when the power supply controlsignal (ICUTX) is activated (L level), so that only the currentregulation resistor (R19) is connected to the fifth terminal. As aresult, the resistance of the current regulation resistor increases.Therefore, the charging current (Iload) supplied to the battery 94 iscompulsorily reduced.

It is thus possible to externally control power supplied to the battery94 using a simple circuit by employing the above-described configurationthat controls the resistance of the current regulation resistor usingthe power supply control signal (ICUTX).

Power supplied to the battery can be controlled using the power supplycontrol signal (signal ICUTX) without changing the internal circuitconfiguration of the charger (charge control IC) 91 included in thecharge control device 92 by employing the above-described configurationthat utilizes an external resistor as the current regulation resistor(note that the invention is not limited thereto) and controls theresistance of the current regulation resistor using the control element(e.g., switching element). Moreover, control such as changing thecharging current in a plurality of stages can be easily implemented byincreasing the number of control elements (M15), for example.

As shown in FIG. 11B, the charger (charge control IC) 91 charges thebattery in a constant current mode in the initial charging stage, andthen transitions to a constant voltage mode.

FIG. 12 is a circuit diagram showing an example of the internal circuitconfiguration of the main portion of the charger (charge control IC)shown in FIG. 11. In FIG. 12, a PMOS transistor (M100) is areference-side transistor of a current mirror, and a PMOS transistor(M200) is an output-side transistor of the current mirror.

The current mirror ratio is set at 1:205, for example. Specifically,when the reference current of the current mirror is referred to as IXand the output current (charging current of the battery) is referred toas IBAT, IBAT=205·IX.

The amount of the reference current IX of the current mirror can beprogrammed (adjusted) by adjusting the resistance of the currentregulation resistors (CRR: R19 and R17), as described above. Therefore,the charging current IBAT (Iload) can be adjusted (reduced, increased,or stopped) by variably adjusting the resistance of the currentregulation resistor (CRR) using the power supply control signal (ICUTX).

The circuit shown in FIG. 12 performs the above-described basic chargingoperation. Since it is necessary to automatically switch the modebetween the constant current mode and the constant voltage mode, asshown in FIG. 11B, a circuit W1, a circuit W2, and a circuit W3 areprovided in the charger (charge control IC) 91.

A constant current source IS is provided so that the gates of thetransistors (M100 and M200) of the current mirror can be pulled down.The constant current source IS may be replaced by a grounded resistor.An NMOS transistor (M160) is a charging-enable transistor.

The circuit W1 is a negative feedback circuit that implementsconstant-current charging, the circuit W2 is a negative feedback circuitthat implements constant-voltage charging, and the circuit W3 is anequalizer that equalizes the potentials of the drains (nodes Y3 and Y4)of the transistors (M100 and M200) of the current mirror.

A comparator CMP10 of the circuit W1 biases the gates of the transistors(M100 and M200) of the current mirror through a diode D100 so that thepotential of a reference-side node Y1 of the current mirror is equal toa first reference potential VREFA. The reference current IX of thecurrent mirror is VREFA/CRR (resistance of the current regulationresistor) (i.e., the reference current IX is made constant). Therefore,the charging current IBAT (Iload) is made constant.

Likewise, a comparator CMP20 of the circuit W2 biases the gates of thetransistors (M100 and M200) of the current mirror through a diode D200so that the potential of an output-side node Y2 of the current mirror isequal to a second reference potential VREFB. In this case, the chargevoltage VBAT is VREFB(1+R300/R400) (i.e., the charge voltage is madeconstant).

Whether the circuit W1 or the circuit W2 is enabled is automaticallydetermined based on the potential of the positive electrode of thebattery 94. Specifically, the output of the comparator CMP20 of thecircuit W2 decreases when the potential of the positive electrode of thebattery 94 is low (initial charging stage). Therefore, the diode D200 isreverse-biased and turned OFF. On the other hand, the diode D100 of thecircuit W1 is forward-biased so that the gates of the transistors (M100and M200) of the current mirror are biased by the circuit W1.

The diode D200 of the circuit W2 is forward-biased when the potential ofthe positive electrode of the battery 94 has increased so that the gatesof the transistors (M100 and M200) of the current mirror are biased bythe circuit W2. In this case, the diode D100 of the circuit W1 isreverse-biased so that the circuit W1 is disabled. Specifically, whenthe potential of the positive electrode of the battery 94 has increasedto a predetermined level (predetermined potential determined by thesecond reference potential VREFB), the mode automatically changes fromthe constant current mode to the constant voltage mode.

In the constant current mode and the constant voltage mode, the chargingcurrent (IBAT or Iload) decreases when the reference current IX of thecurrent mirror is reduced to a large extent using the power supplycontrol signal (ICUTX), for example. As a result, the load state of thebattery is compulsorily reduced by external control.

Example That Controls Battery Charging Utilizing Negative FeedbackControl Circuit of Charger (Charge Control IC)

FIG. 13 is a circuit diagram illustrative of an example of a specificinternal configuration and operation of the charge control device 92.

In the charge control device 92 shown in FIG. 13, a reference voltage(Vref) of a negative feedback control circuit for constant currentcontrol (or constant voltage control) is adjusted using the power supplycontrol signal (ICUTX) to decrease (or increase) the charging current(load current).

The battery 94 shown in FIG. 13 includes a secondary battery QP and acharging current detection resistor (current/voltage conversionresistor) R16.

The charge control device (IC) 92 shown in FIG. 13 includes a PMOStransistor M10 (charging current regulation element) that functions as apower supply control circuit 99, a comparator CP1, and a referencevoltage generation circuit 97. The charge control device (IC) 92normally includes a CPU (not shown in FIG. 13) in order to implementhighly accurate control.

The reference voltage (Vref) is supplied to an inverting terminal of thecomparator CP1, and a voltage across the resistor R16 is supplied to anon-inverting terminal of the comparator CP1. The gate of the PMOStransistor 99 is driven based on an output signal from the comparatorCP1, whereby the amount of current (charging current) supplied to thebattery 94 is adjusted. In this case, since the voltage across theresistor R16 is made equal to the reference voltage Vref by negativefeedback control, negative feedback control is performed so that acurrent (charging current) that flows through the resistor R16 is equalto a current corresponding to the reference voltage Vref.

A charging voltage supplied to the secondary battery QP can be adjustedto the reference voltage Vref by supplying the voltage of the positiveelectrode of the secondary battery QP to the non-inverting terminal ofthe comparator CP1 (this configuration is not shown).

The reference voltage generation circuit 97 includes a Zener diode D10,voltage-divider resistors R12 and R13, a resistor R14 and a PMOStransistor M12 for adjusting the reference voltage.

A resistor R10 and the Zener diode D10 form a constant voltage circuit.A cathode voltage of the Zener diode D10 is divided by the resistors R12and R13, and serves as the reference voltage (Vref) input to theinverting terminal of the comparator CP1.

For example, the NMOS transistor M12 is turned OFF when the voltagesupply control signal (ICUTX) from the power reception control device 50(power-reception-side control circuit 52) is set at the low level.Therefore, a voltage obtained by dividing the cathode voltage of theZener diode D10 using the resistors R12 and R13 serves as the referencevoltage (Vref).

The NMOS transistor M12 is turned OFF when the voltage supply controlsignal (ICUTX) is set at the high level. Therefore, the resistors R14and R13 are connected in parallel so that a combined resistor formed bythe resistors R14 and R13 (the resistance of the combined resistor issmaller than the resistance of the resistor R13) and the resistor R12are connected in series. Accordingly, the voltage level of the referencevoltage Vref decreases so that the charging current Iload supplied tothe battery 94 is reduced (including the case where the charging currentis stopped), whereby the load is reduced.

Note that the above-described operation is merely an example. Theinvention is not limited thereto. Various embodiments may be employedfor controlling the charging current Iload using negative feedbackcontrol. The charging current may be increased instead of reducing thecharging current. The voltage level of the reference voltage may bechanged in a plurality of stages.

In the above-described example, the reference voltage (Vref) of thecomparator CP1 is adjusted. Note that the voltage (control targetvoltage) input to the non-inverting terminal of the comparator CP1 maybe changed using the power supply control signal (signal ICUTX) withoutadjusting the reference voltage.

Since the charge control device 92 shown in FIG. 13 increases ordecreases (adjusts) the charging current by controlling the operation ofthe negative feedback control circuit using the signal ICUTX, the amountof charging current can be controlled with high accuracy. Since thenegative feedback control circuit originally provided in the chargecontrol device 92 for implementing constant current control and constantvoltage control is effectively utilized, load imposed on the circuit isreduced while facilitating implementation.

Example That Controls Charging Current by Providing Power SupplyRegulation Circuit (e.g., Current Limiting Element) in Charging Path

FIG. 14 is a circuit diagram illustrative of another example of aspecific internal configuration and operation of the charge controldevice 92.

The charge control device 92 shown in FIG. 14 employs a configuration inwhich a PMOS transistor M14 (current limiting element) that functions asa power supply regulation circuit 101 is provided in the power supplypath, and the operation of the PMOS transistor M14 is controlled usingthe power supply control signal (ICUTX).

For example, when the voltage supply control signal (ICUTX) is set atthe high level (during normal operation), a signal reversed using aninverter INV1 is applied to the gate of the PMOS transistor M14 so thatthe PMOS transistor M14 is completely turned ON, whereby the chargingcurrent Iload is supplied to the battery 94.

When the power supply control signal (ICUTX) is set at the low level(during load reduction), the PMOS transistor M14 is set in a half ONstate (i.e., a conducting state between a completely OFF state and acompletely ON state) or is turned OFF so that the charging current Iloadis reduced to implement a low-load state or a no-load state. Thisembodiment has an advantage in that the circuit configuration is notcomplicated.

The charge control device 92 shown in FIG. 14 includes a negativefeedback control circuit similar to that shown in FIG. 13. Therefore,the charge control device 92 shown in FIG. 14 can control the chargingcurrent with high accuracy during normal operation in the same manner asin FIG. 13.

Second Embodiment

This embodiment illustrates a series of sequences of the non-contactpower transmission system shown in FIGS. 1 and 3.

Operation of Non-Contact Power Transmission System

FIG. 15 is a flowchart showing an outline of an example of the operationof the power transmission device. The operation of the powertransmission device 10 is roughly divided into a check on the powertransmission target before power transmission (step SA) and a check onthe power transmission environment during power transmission (includingbefore power transmission) (step SB) (these steps are enclosed by bolddotted lines).

The power transmission device 10 starts temporary power transmissionwhen the switch (SW) has been turned ON, as described above (steps S1and S2).

The power transmission device 10 then checks whether or not thepower-reception-side instrument (510) is placed at an appropriateposition (step S3), and performs ID authentication on thepower-reception-side instrument 510 (power reception device 40) todetermine whether or not the power-reception-side instrument 510 is anappropriate power transmission target (step S4). A situation in whichthe user must again turn ON the switch (SW) due to an accidental errorin ID authentication is prevented by allowing retries during IDauthentication. This improves convenience to the user.

When the power transmission device 10 has failed in position detectionor ID authentication (step S5), the power transmission device 10 stopstemporary power transmission, and returns to the initial state in whichthe power transmission device 10 waits for the switch to be turned ON(i.e., a state in which the power transmission device 10 waits for thestep S1 to occur).

The position detection circuit 56 included in the power reception device40 shown in FIG. 2 checks whether or not the power-reception-sideinstrument is placed at an appropriate position (position detection)based on the waveform monitor signal (PHIN) of the induced voltagesignal in the primary coil (L1) or a direct-current voltage (ADIN)obtained by rectifying the induced voltage in the secondary coil (L2).

FIG. 21 is a view illustrative of the principle of position detection.As shown in FIG. 21, the waveform (peak value) of the signal PHIN andthe voltage level of the signal ADIN change corresponding to thepositional relationship between the primary coil (L1) and the secondarycoil (L2).

For example, when performing position detection based on the signalADIN, a direct-current voltage (ADIN) at a given level (V3 level) cannotbe obtained when the power-reception-side instrument is placed at aninappropriate position (i.e., the power-reception-side instrument isdetermined to be placed at an inappropriate position). The positiondetection result may be transmitted from the power-reception-sideinstrument to the power-transmission-side instrument utilizing loadmodulation, for example. The power-reception-side instrument may notifythe power-transmission-side instrument that the power-reception-sideinstrument is placed at an inappropriate position by not transmitting IDauthentication information to the power-transmission-side instrumentwithin a given period of time after receiving temporary powertransmission.

Again referring to FIG. 15, the power transmission device 10 startsnormal power transmission (charge power transmission) after IDauthentication (step S6). The power transmission device 10 detectswhether or not a metal foreign object is present (metal foreign objectdetection) (step S7), and detects whether or not a takeover state hasoccurred (takeover state detection) by means of regular load changedetection (steps S8 and S9). The power transmission device 10 detectswhether or not the power-reception-side instrument has been removed(leave detection) (step S10), detects whether or not the switch has beenturned OFF (switch OFF detection) (step S11), and detects whether or nota full-charge notification (power transmission stop request) has beenreceived (full-charge notification detection) (step S12). When the powertransmission device 10 has detected one of the above-mentioned states(step S13), the power transmission device 10 stops normal powertransmission (step S14), and returns to the initial state (i.e., a statein which the power transmission device 10 waits for the step Si tooccur).

Whether or not a metal foreign object is present (step S7) and whetheror not a takeover state has occurred (step S10) may be detected based ona change in waveform of an induced voltage signal of the primary coil(L1). FIGS. 22A to 22F are views illustrative of the principle of metalforeign object (conductive foreign object) detection. FIGS. 22B to 22Fshow changes in an induced voltage signal (V(NA2)) of the primary coil(L1) shown in FIG. 22A corresponding to the relative position betweenthe primary coil and a metal foreign object MET (small or medium-sizedconductive foreign object).

As shown in FIGS. 22B to 22F, the waveform (amplitude) of the inducedvoltage signal V(NA2) when the metal foreign object MET is absent (FIG.22F) differs from the waveform (amplitude) of the induced voltage signalV(NA2) when the metal foreign object (MET) is present (FIGS. 22B to22E). Therefore, the presence or absence of the metal foreign object(MET) can be detected by monitoring the waveform of the induced voltagesignal V(NA2) of the primary coil (L1) using the waveform monitoringcircuit 14 (see FIG. 4). The term “waveform monitoring” includesmonitoring the amplitude or monitoring the phase of the current orvoltage, and the like.

FIGS. 23A to 23D are views illustrative of the principle of removal(leave) detection. When the power-reception-side instrument 510 isplaced as shown in FIG. 23A, the induced voltage signal V(NA2) of theprimary coil (L1) has a waveform shown in FIG. 23B. When thepower-reception-side instrument 510 has been removed (leave) (see FIG.23C), the primary coil and the secondary coil are decoupled, so that themutual inductance due to coupling is lost, and a resonance occurscorresponding to only the inductance of the primary coil. As a result,since the resonance frequency increases and approach the transmissionfrequency, a current easily flows through the power transmission coil,whereby the load with respect to the power-transmission-side instrumentincreases (i.e., the induced voltage increases). Specifically, thewaveform of the induced voltage signal of the primary coil changes.

Specifically, the induced voltage signal V(NA2) of the primary coil (L1)has a waveform shown in FIG. 23D. The waveform (amplitude) shown in FIG.23D clearly differs from the waveform shown in FIG. 23B. Therefore,whether or not the power-reception-side instrument has been removed canbe detected by monitoring the waveform of the induced voltage signalV(NA2) of the primary coil (L1) using the waveform monitoring circuit 14(see FIG. 3). Therefore, removal of the power-reception-side instrumentcan be detected using a circuit having a simple configuration byutilizing this principle. Unnecessary power consumption does not occurby detecting removal (leave) of the power-reception-side instrumentduring normal power transmission. Therefore, a reduction in powerconsumption and an improvement in safety and reliability can beachieved.

Example of Configuration of Power-Transmission-Side Control Circuit

FIG. 16 is a circuit diagram showing an example of the configuration ofthe power-transmission-side control circuit. As shown in FIG. 16, thepower-transmission-side control circuit 22 includes a logic circuit 100.

The logic circuit 100 includes a noise removal circuit 102 that removesnoise which occurs when the switch SW is turned ON/OFF, a flip-flop(F/F) 104 that stores whether the present state is the powertransmission state or the initial state, a position detection section106, an ID authentication section 108, a removal (leave) detectionsection 110, a foreign object detection section 112 (including atakeover state detection section 114), a full-charge notification (powertransmission stop request) detection section 116, and a powertransmission control section 118 that ON/OFF-controls power transmissionbased on the detection result of each section.

Basic Sequence Example of Non-Contact Power Transmission System

FIG. 17 is a view showing a basic sequence example of the non-contactpower transmission system. The switch SW is provided on thepower-transmission-side electronic instrument (power-transmission-sideinstrument) 500 (see left). The user places the power-reception-sideelectronic instrument (power-reception-side instrument) 510 at apredetermined position, and presses the switch SW. The powertransmission device 10 starts temporary power transmission based on anedge (e.g., negative edge NT) which occurs when the user has pressed theswitch SW as a trigger (S20), and performs position detection (stepS21). When the power-reception-side instrument 510 is placed at aninappropriate position, the power transmission device 10 stops temporarypower transmission (step S22).

When the power-reception-side instrument 510 is placed at aninappropriate position, the power transmission device 10 performs IDauthentication (step S23). Specifically, ID authentication information(e.g., manufacturer information, instrument ID number, and ratinginformation) is transmitted from the power-reception-side instrument tothe power-transmission-side instrument. Since ID authentication may failaccidentally, it is preferable to allow a given number of (e.g., three)retries taking convenience to the user into account, and determine thatID authentication has failed when failure (NG) has occurred successively(step S24).

After ID authentication, the power transmission device 10 starts normalpower transmission for the power reception device 40 (step S26). Whenthe power transmission device 10 has detected that the switch (SW) hasbeen pressed (turned OFF) during normal power transmission (step S27),the power transmission device 10 stops normal power transmission andreturns to the initial state (step S28).

The power transmission device 10 performs removal detection (step S29),metal foreign object detection (step S30), secondary-side regular loadauthentication (including a secondary-side load reduction process: stepS31), and takeover state detection (step S32), and stops normal powertransmission when one of these states has been detected (step S33). Theterm “load reduction” accompanying secondary-side regular loadauthentication refers to a process that reduces (or stops) powersupplied to the battery when performing load modulation to apparentlyreduce the load state of the battery, since the primary-side instrumentmay not successfully receive a modulation signal when load modulation isperformed in a state in which the load state of the battery is heavy.

In FIG. 17, when the power reception device 40 has detected that afull-charge state has occurred, the power reception device 40 creates afull-charge notification (save frame; power transmission stop requestframe) and transmits the full-charge notification to thepower-transmission-side instrument (step S34). When the powertransmission device 10 has detected the full-charge notification (powertransmission stop request frame) (step S35), the power transmissiondevice 10 stops normal power transmission and returns to the initialstate (step S36).

FIG. 18 is a state transition diagram showing the state transition ofthe non-contact power transmission system that performs the sequenceshown in FIG. 17. As shown in FIG. 18, the state of the non-contactpower transmission system is roughly divided into an initial state (idlestate: ST1), a position detection state (ST2), an ID authenticationstate (ST3), a power transmission (normal power transmission) state(ST4), and a regular load authentication state (ST5) (and a loadreduction state (ST6)).

The non-contact power transmission system transitions from the state ST1to the state ST2 when the switch has been turned ON (Q1), and returns tothe state ST1 (Q2) when the position detection result is inappropriate(NG). When the position detection result is appropriate (OK), thenon-contact power transmission system monitors whether or not IDauthentication successively fails a plurality of times (Q4). When IDauthentication has successively failed (Q5), the non-contact powertransmission system transitions to the state ST1. When ID authenticationhas succeeded (Q6), the non-contact power transmission systemtransitions to the state ST4.

The non-contact power transmission system performs switch (SW) OFFdetection (Q7), removal detection (Q12), metal detection (Q10), takeoverstate detection (Q17), and full-charge detection (Q14). The non-contactpower transmission system returns to the initial state when one of thesestates has been detected (Q8, Q9, Q11, Q13, or Q15).

Since the non-contact power transmission system that performs the basicsequence shown in FIG. 17 starts power transmission when the switch hasbeen turned ON, a reduction in power consumption and an improvement insafety can be achieved.

Since the non-contact power transmission system stops power transmissionand returns to the initial state (switch ON wait state) when thenon-contact power transmission system has received the full-chargenotification (power transmission stop request), unnecessary powertransmission does not occur. Therefore, a reduction in power consumptionand an improvement in safety can be achieved.

Since normal power transmission is performed after ID authentication hasbeen completed successfully, power is not transmitted to aninappropriate instrument. Therefore, reliability and safety areimproved.

Various detection operations (i.e., removal detection, metal foreignobject detection, takeover state detection based on secondary-sideregular load authentication, and full-charge detection) are performedduring normal power transmission, and normal power transmission ispromptly stopped and the initial state is recovered when one of thesestates has been detected. Therefore, unnecessary power transmission doesnot occur while taking all possible measures against a foreign object.This implements a system with extremely high reliability (safety).

FIGS. 19 and 20 are flowcharts showing an operation example of thenon-contact power transmission system that performs the basic sequenceshown in FIG. 17. In FIGS. 19 and 20, a primary-side operation flow isshown on the left, and a secondary-side operation flow is shown on theright.

As shown in FIG. 19, when the switch SW has been turned ON (step S40),the power-transmission-side instrument starts temporary powertransmission (e.g., the transmission frequency is f1; step S41), and atimer starts a count operation (step S42).

The power-reception-side instrument transitions from a standby state(step S60) to a power-ON state (step S61) when the power-reception-sideinstrument has received temporary power transmission, and determines theposition level (position detection). When the position level isinappropriate (NG), the power-reception-side instrument returns to theinitial state (step S60). When the position level is appropriate (OK),the power-reception-side instrument creates the ID authentication frame(S63), and transmits the ID authentication frame (step S64).

The power-transmission-side instrument receives the ID authenticationframe (step S44), and determines whether or not a time-out has occurred(step S43). When the power-transmission-side instrument cannot receivethe ID authentication frame within a given period of time, thepower-transmission-side instrument stops power transmission (step S49).

When the power-transmission-side instrument has received the IDauthentication frame within a given period of time, thepower-transmission-side instrument performs a frame authenticationprocess (step S45). When authentication has succeeded (OK), thepower-transmission-side instrument transmits a permission frame to thepower-reception-side instrument (step S47). When authentication hasfailed (NG), the power-transmission-side instrument stops powertransmission (step S51).

The power-reception-side instrument checks the permission frametransmitted from the power-transmission-side instrument (step S65), andtransmits a start frame to the power-transmission-side instrument (stepS66).

The power-transmission-side instrument checks the start frame (stepS48), enables regular load change detection (takeover state detection)(step S49), and starts charge power transmission (normal powertransmission) (step S50).

The power-reception-side instrument receives charge power transmission(normal power transmission), and starts charging the battery (step S67).

FIG. 20 shows the subsequent flow. The power-transmission-sideinstrument waits for the full-charge notification (power transmissionstop request) from the power-reception-side instrument (step S71) whileperforming removal detection, metal foreign object detection, takeoverstate detection, and switch OFF detection (step S70).

The power-reception-side instrument performs regular load modulation fortakeover detection while charging the battery (step S80), and detectswhether or not the battery has been fully charged (step S81). When thepower-reception-side instrument has detected that the battery has beenfully charged, the power-reception-side instrument transmits thefull-charge notification frame (save frame; power transmission stoprequest) to the power-transmission-side instrument (step S82).

When the power-transmission-side instrument has received the full-chargenotification frame (save frame; power transmission stop request) fromthe power-reception-side instrument, the power-transmission-sideinstrument disables regular load change detection (step S72), and stopspower transmission (step S73).

The non-contact power transmission system according to theabove-described embodiments that performs the above-described operationsachieves the following main effects. Note that the following effects arenot necessarily achieved at the same time.

(1) Since the non-contact power transmission system starts powertransmission when the switch has been turned ON, a reduction in powerconsumption and an improvement in safety can be achieved.

(2) The switch is utilized so that the user turns the switch ON afterplacing the secondary-side instrument or places the secondary-sideinstrument after turning ON the switch, for example. In either case,since power transmission (including temporary power transmission) startswhen the user has turned the switch ON (i.e., the user has indicated hisintention to start charging), a situation in which power transmissionstarts by surprise is prevented so that the user feels more reassured.When the secondary-side instrument has been placed, the switch may beturned ON due to the weight of the secondary-side instrument. In thiscase, the user need not turn the switch ON.

(3) Since the non-contact power transmission system stops powertransmission and returns to the initial state (switch ON wait state)when the non-contact power transmission system has received thefull-charge notification (power transmission stop request), unnecessarypower transmission does not occur. Therefore, a reduction in powerconsumption and an improvement in safety can be achieved.

(4) Since normal power transmission is performed after ID authenticationhas been completed successfully, power is not transmitted to aninappropriate instrument. Therefore, reliability and safety areimproved.

(5) Various detection operations (i.e., removal detection, metal foreignobject detection, takeover state detection based on secondary-sideregular load authentication, and full-charge detection) are performedduring normal power transmission, and normal power transmission ispromptly stopped and the initial state is recovered when one of thesestates has been detected. Therefore, unnecessary power transmission doesnot occur while taking all possible measures against a foreign object.This implements a system with extremely high reliability (safety).

Although only some embodiments of the invention have been described indetail above, those skilled in the art would readily appreciate thatmany modifications are possible in the embodiments without materiallydeparting from the novel teachings and advantages of the invention.Specifically, many modifications are possible without materiallydeparting from the novel teachings and advantages of the invention.

Accordingly, such modifications are intended to be included within thescope of the invention. Any term (e.g., GND and portabletelephone/charger) cited with a different term (e.g., low-potential-sidepower supply and electronic instrument) having a broader meaning or thesame meaning at least once in the specification and the drawings can bereplaced by the different term in any place in the specification and thedrawings. Any combinations of the embodiments and the modifications arealso included within the scope of the invention.

The configurations and the operations of the power transmission controldevice, the power transmission device, the power reception controldevice, and the power reception device and the method of detecting thesecondary-side load by the primary side instrument are not limited tothose described in the above embodiments. Various modifications andvariations may be made.

The invention achieves the effect of providing a highly reliablenon-contact power transmission system with low power consumption.Therefore, the invention is useful for a power transmission controldevice (power transmission control IC), a power transmission device(e.g., IC module), a non-contact power transmission system, and anelectronic instrument (e.g., portable terminal and charger). Note thatthe term “portable terminal” includes a portable telephone terminal, aPDA terminal, and a portable computer terminal.

What is claimed is:
 1. A power reception device included in anon-contact power transmission system that performs non-contact powertransmission from a power transmission device to the power receptiondevice through a primary coil and a secondary coil that areelectromagnetically coupled, the power reception device supplying acharging power to a battery device that includes a battery and a chargecontrol device that controls charging of the battery, the powerreception device comprising: a power reception section that converts aninduced voltage in the secondary coil into a direct-current voltage; apower-reception-side control circuit that controls an operation of thepower reception device; a load modulation section that includes a loadmodulation transistor and modulates a load of the power receptiondevice; and a power supply control signal output terminal that includesa power supply control transistor and supplies to the charge controldevice a power supply control signal configured to control powersupplied to the battery device, wherein the load modulation sectiontransmits information from the power reception device to the powertransmission device through the primary coil and the secondary coilutilizes load modulation of the load, and the power-reception-sidecontrol circuit controls the load modulation transistor of the loadmodulation section, the power supply control transistor of the powersupply control section, and the power reception control circuit thatON/OFF-controls the load modulation transistor and the power supplycontrol transistor.
 2. The power reception device as defined in claim 1,further comprising a series regulator having an input terminal and anoutput terminal, and the voltages at the input terminal and the outputterminal of the series regulator being input to the power-reception-sidecontrol circuit through signal lines so that load state of the batteryincluded in the battery device can be detected by monitoring the voltageacross the series regulator.
 3. The power reception device as defined inclaim 1, the power transmission device detecting a peak value of theinduced voltage in the primary coil using a waveform detection circuitand detecting a change in the load of the power reception device using apower-transmission-side control circuit.
 4. The power reception deviceas defined in claim 1, the power reception device modulating the loadduring the power transmission and transmitting a foreign objectdetection pattern to the power transmission device.
 5. The powerreception device as defined in claim 1, the information beingtransmitted from the power transmission device instrument to the powerreception device utilizing frequency modulation.
 6. The power receptiondevice as defined in claim 1, the information being transmitted from thepower reception device instrument to the power transmission deviceutilizing load modulation.
 7. A power reception device included in anon-contact power transmission system that performs non-contact powertransmission from a power transmission device to the power receptiondevice through a primary coil and a secondary coil that areelectromagnetically coupled, the power reception device supplying acharging power to a battery device that includes a battery and a chargecontrol device that controls charging of the battery, the powerreception device comprising: a power reception section that converts aninduced voltage in the secondary coil into a direct-current voltage; apower-reception-side control circuit that controls an operation of thepower reception device; a load modulation section that modulates a loadof the power reception device; a charge detection circuit that detects acharge state; a power supply control signal output terminal thatsupplies to the charge control device a power supply control signalconfigured to control power supplied to the battery device; and aterminal that receives a charge detection signal from the batterydevice, wherein the load modulation section transmits information fromthe power reception device to the power transmission device through theprimary coil and the secondary coil utilizes load modulation of theload, and the power-reception-side control circuit controls the powersupply control signal to reduce or stop the charging power supplied tothe battery through the charge control device when thepower-reception-side control circuit controls the load modulationsection to transmit the information from the power reception device tothe power transmission device, and the charge detection circuitdetecting the charge state by detecting whether a light-emitting deviceused to indicate the charge state is turned ON or OFF.
 8. The powerreception device as defined in claim 7, the power reception devicecontrolling power supplied to the battery by a power supply controlsignal based on a battery control command issued from the powertransmitting device to the power reception device.
 9. The powerreception device as defined in claim 7, the information beingtransmitted from the power transmission device instrument to the powerreception device utilizing frequency modulation.
 10. The power receptiondevice as defined in claim 7, the information being transmitted from thepower reception device instrument to the power transmission deviceutilizing load modulation.
 11. An electronic instrument comprising: thepower reception device as defined in claim 1, wherein the battery devicereceives power from the power reception device.
 12. A non-contact powertransmission system comprising: the power reception device as defined inclaim 1; the power transmission device; the primary coil; and thesecondary coil.